1. Field of the Invention
This invention relates to a structural corner reinforcement for architectural or structural members such as frame sections or frames for screens, windows, doors, shutters, plastic panels, and the like, a frame including such a structural reinforcement and methods of manufacturing these products.
2. Description of the Related Art
For convenience of discussion, the invention will be defined and described with particular reference to structural reinforcements for use in frame sections or frames. Nevertheless, it will be understood that the invention is of general utility.
Frames for screens, windows, doors, shutters, plastic panels and the like are commonly made of four elongated frame members of uniform cross section connected together by corner assemblies. These frame members are typically roll-formed from aluminum or sheet steel, although some may be extruded plastic or aluminum, and some of these frame members are foam-filled to increase their strength. For example, U.S. Pat. No. 3,885,371 shows a roll-formed sheet metal window frame filled with a rigid lightweight foamed material such as polyurethane.
These frames must have adequate strength as well as longitudinal and torsional rigidity, and the corners and joints must be rigid. These frames also must be durable and resist impact, damage and corrosion. Further, these frames must meet at least these practical requirements without excessive weight or cost.
For example, in the case of large screen frames, particularly those used for patio door screens, prior corner connectors have been inadequate to sufficiently prevent twisting or bending of the frame. The twisting or bending of the frame out of its plane is particularly troublesome when the frame is removed from its support framing, for maintenance or cleaning, and then an attempt is made to replace it. The twisting or bending also presents problems during normal operation if the frame binds in its support tracks.
U.S. Pat. No. 4,570,406 shows an inexpensive, molded plastic corner connector key, which frictionally interconnects with the end portions of conventional screen frame members that can be square cut rather than mitered. The corner connector itself forms the exposed corner of the frame and thus is sized and shaped to match or blend with the ends of the frame members to form a visually uniform frame. The connector key has two rectangular, tubular-shaped legs arranged at right angles. The legs integrally fit within and are frictionally locked in face-to-face contact against the interior wall surfaces of the frame members.
U.S. Pat. No. 5,431,211, commonly assigned to the assignee of the subject application, shows a corner assembly for a window screen frame. The corner assembly has a pair of connector arms extending outwardly from a corner connector, generally at ninety degrees relative to each other. The connector arms are telescopically received in gripping relation within corresponding channels of side members of the frame.
U.S. Pat. No. 4,651,482 shows a corner piece for connecting adjacent hollow frame members to form a frame used in the construction of thermally insulated windows. The corner piece includes horizontal and vertical legs formed at a right angle. One end of each leg has a cutting edge. When the ends of each leg are inserted into a hollow frame member, which has internal partitions, the sharpened cutting edge is able to cut around the adjacent partition to enter the frame member. Sealant may be injected into the corner pieces and the frame members after assembly to seal off any gaps around the installed corner piece.
The foregoing corner connectors have a significant drawback, however, in that wedging the corner piece into the frame member can deform the frame member. This may result in jamming of the frame member during movement in its track or guide. Also, these current corner connectors concentrate loading of force at the points of contact, rather than distributing the loading. Such point loading results in local, permanent deformation of the light gauge metal frame members near the point loads. Once permanent deformation occurs, a clearance gap is formed, which allows movement (i.e., play) between the corner insert and the frame member. This play lessens the stiffness of the corner connection and the integrity of the entire frame assembly. Once clearance is established, and movement allowed, the connection is "worked" in operation and clearances increase further. To reduce the local deformation, thicker gauge frame members are required. This increases costs.
The initial clearances that are required between the corner insert and the frame members in order to insert current corner connectors also can reduce corner rigidity and torsional strength. A certain clearance is necessary to allow easy, hand assembly of the corner insert in the frame assembly. Although a snug fit is desired, practical stamping/molding and roll-forming tolerances allow play, which should be avoided, as discussed above. To reduce this play, and to prevent the corner connector from sliding out, some have proposed bending portions of the aluminum roll-formed section of the frame into pre-cut holes in the metal corner connector. This is known as staking.
Patio doors, in order to slide in their tracks, are usually provided with wheels mounted at the four corners of the door frame. For example, U.S. Pat. No. 3,729,868 shows a screen door having L-shaped corner connectors that include extensions which frictionally fit into interior spaces of the door frame. A sidewall of each connector is aligned with a rail of the door frame and includes a cutout that enables a guide roller or wheel to protrude therethrough. The roller is mounted to a bracket in a hollow interior space of the connector and pivots about a pin anchored in the connector. A leaf spring biases the roller into the rail of the door frame. The device in the '868 patent, while simplifying construction of the screen door, does not provide a frame having adequate strength and longitudinal and torsional rigidity, especially at the corners.
Accordingly, a need has arisen for a structural corner reinforcement and a frame including such a reinforcement, which overcome the drawbacks noted above with respect to conventional corner assemblies. There is an additional need for methods of making these products.